This invention relates to an improved structure of connection between a bus bar (constituting an internal circuitry of an electric connection box) and a press-connecting branch terminal in the electric connection box used to interconnect wire harnesses or the like.
There are known many electric connection boxes, such as a fuse box used in a vehicle or a branch connection box, which includes branch connections of a wire harness, and in order to simplify a wiring pattern, a branch circuit is formed in a concentrated manner.
The formation of a branch circuit is made either by a method in which upstanding branch tabs are formed directly from a bus bar, constituting an internal circuit, in continuous relation to the bus bar, or by a method in which there is used a press-connecting branch terminal having a branch tab at one side and a press-connecting portion at the other side which has a U-shaped slot, and an electric wire or a bus bar is press-fitted in the slot for connection.
FIGS. 10 and 11 show the prior art (Japanese Laid-Open Patent Application No. 45575/86) relating to the formation of such branch circuit.
As shown in FIG. 10, a press-connecting branch terminal a has one or more branch tabs b at one side and a press-connecting portion c at the other side which has a U-shaped slot d.
As shown in FIG. 11, the branch tab b of each press-connecting terminal a is passed through in an insertion hole h formed in a bottom of a housing g of an upper case e, and is press-fitted at its proximal portion in this insertion hole, thus fixing the branch tab. Then, a group of connection electric wires i taken, for example, form a wire harness are disposed in parallel relation between the upper case e and a lower case f, and each connection wire i is press-fitted in a desired U-shaped slot d for connection, thereby forming a branch circuit in a concentrated manner.
FIG. 12 shows a branch connection between a press-connecting terminal a' and a bus bar j (Japanese Laid-Open Patent Application No. 131483/87).
The press-connecting terminal a' has a pair of opposed press-connecting portions c' each having a U-shaped slot d', and the distal end of an opening O of the slot d' is enlarged by a tapered configuration O' to provide an insertion guide by which the connection can be effected even when the center line of the bus bar j is slightly out of registry with (that is, displaced from) the center line of the opening O.
In the prior art structure shown in FIG. 11, the press-connecting terminal a is press-fitted in and fixed to the insertion hole h. If the branch tab b is twisted, for example, when attaching an external connector to the housing g, there is a risk that this force is applied directly to a point of contact between the tab and the electric wire i. Further, the press-connecting terminal a is press-fitted and fixed at its portion indicated by thickened lines P. If the overall length L of the press-connecting terminal a is increased, it is necessary to increase the thickness of a resin layer of the upper case e, and therefore the cover becomes bulky. Further, the press-connecting terminal a is required to have a terminal width l commensurate with the value of electric current. Thus, in addition to the above necessity of increasing the thickness of the resin layer for press-fitting and fixing, the required width l is needed for securing electric current, and therefore the upper case e is still more bulky.
In the branch connection construction shown in FIG. 12, the guide (tapered portion O') for the bus bar j is provided on the press-connecting terminal a', and therefore reaction forces, resulting from corrections of the angle and position displacement of the bus bar j, act directly on the press-connecting portion, which may result in failure to achieve a proper press-connection by a resilient nature of the press-connecting portion , which may result in failure to achieve a proper press-connection by a resilient nature of the press-connecting portion c'.